393
FXUS21 KWNC 061901
PMDTHR
US Hazards Outlook
NWS Climate Prediction Center College Park MD
300 PM EST November 06 2025

SYNOPSIS: Mid-level low pressure is forecast to approach the West Coast later
next week and then eventually shift eastward over the West by November 17 or
18. This would increase the risk of multiple hazards from the West Coast to
inland areas of the West. Although low pressure development is expected to
occur across the Great Plains during week-2, precipitation amounts for the
central U.S. are highly uncertain. Despite favored wetness throughout southern
Alaska from November 14-20, precipitation amounts are expected to remain below
hazardous thresholds.



HAZARDS

Moderate risk of heavy precipitation for southern California, Fri-Sat, Nov
14-15.

Moderate risk of heavy precipitation for the foothills of the Sierra Nevada
Mountains, Fri-Sun, Nov 14-16.

Slight risk of heavy precipitation for portions of California and the Pacific
Northwest, Fri-Sun, Nov 14-16.

Slight risk of heavy precipitation for parts of Arizona, Sat-Sun, Nov 15-16.

Moderate risk of heavy snow for the Sierra Nevada Mountains, Fri-Sun, Nov 14-16.

Slight risk of heavy snow for portions of the Cascades, Sierra Nevada, and

Klamath Mountains, Fri-Sun, Nov 14-16.

Slight risk of heavy snow for portions of the Northern and Central Rockies and

Wasatch Range, Fri-Tue, Nov 14-18.

Slight risk of heavy snow for the Mogollon Rim of Arizona, Sat-Sun, Nov 15-16.

Slight risk of high winds from the Rockies to the Great Plains and Upper
Mississippi Valley, Fri-Tue, Nov 14-18.

DETAILED SUMMARY

FOR SUNDAY NOVEMBER 09 - THURSDAY NOVEMBER 13:
https://www.wpc.ncep.noaa.gov/threats/threats.php

FOR FRIDAY NOVEMBER 14 - THURSDAY NOVEMBER 20: The ECENS and GEFS have slowed
the eastward progression of the 500-hPa longwave trough nearing the West Coast
by one day compared to previous model runs, while the CMCE remains the fastest
solution with this trough axis shifting east to the Rockies by day 9, November
15. Despite these model differences on the timing of when this trough moves
inland, there remains an increased risk of heavy precipitation and mountain
snow for the West. Since the uncalibrated ECENS (GEFS) depicts a 40-50 (30-40)
percent chance of more than one inch of precipitation for southern California
early in week-2, a moderate risk of heavy precipitation is maintained for that
part of the state. It is now valid through November 15 given the slower model
trend. Locally heavy precipitation would elevate the risk of urban flash
flooding and mudslides in burn scar areas across southern California. The
moderate risk of heavy precipitation was discontinued for northern California
as the ECENS and GEFS Probabilistic Extremes Tools (PETs) have less than a 40
percent chance that 3-day amounts exceed the 85th percentile, but these PETs
and uncalibrated 24-hour amounts from the GEFS and ECENS support maintaining
the moderate risk for the foothills of the Sierras from November 14-16. For the
same time period, the ECENS depicts near a 40 percent chance of more than a
foot of snow for the Sierra Nevada Mountains which are designated with a
moderate risk of heavy snow. By November 17, the longwave trough axis is
expected to shift inland from the West Coast and based on guidance from the
Integrated Vapor Transport tool, the slight risks of heavy precipitation and
heavy snow for California and the Pacific Northwest ends on November 16.



As 500-hPa heights fall and anomalous mid-level troughing becomes established
over the West, there is likely to be a period of snowfall across the northern
to central Rockies and Wasatch Mountains of Utah beginning on November 14 and
lasting through the 18th. Although model solutions differ on how the 500-hPa
longwave pattern evolves during mid-November, the ECENS and GEFS agree that
mountain snowpack will likely increase prior to Thanksgiving. Accumulating snow
could even occur at lower elevations of the Great Basin once the amplified
trough shifts well inland. Due to a predicted lack of strong onshore flow, the
wind hazard was discontinued along the West Coast. However, a deepening
longwave trough over the interior West and potential for leeside surface low
development support a slight risk of high winds from the Rockies east to the
Great Plains and Upper Mississippi Valley from November 14 to 18.



A shortwave trough may dig southward to the Desert Southwest which would result
in an increased chance of heavy precipitation across Arizona early in week-2.
Although overall the model guidance has backed off on the intensity of this
shortwave trough and its associated precipitation amounts, the ECENS PET still
supports a slight risk of heavy precipitation for parts of Arizona, valid on
November 15 and 16. Consistent with the enhanced precipitation signal, a slight
risk of heavy snow is posted for the Mogollon Rim of Arizona on the same days.



Downstream of the 500-hPa trough axis over the West, there is an increased
chance of surface low development across the Great Plains. This surface low
would then most likely track northeastward to the Upper Mississippi Valley or
Great Lakes. Given the anomalous warmth preceding any low pressure system and
lack of any strong cold air advection behind it, heavy snowfall across the
north-central U.S. is not a concern at this time. The ECENS and GEFS are
beginning to show a weak signal for heavy precipitation across either the
Mississippi or Ohio Valley, but varying placement of the heaviest precipitation
amounts precludes designation of a slight risk of heavy precipitation at this
time.

FORECASTER: Brad Pugh

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